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Explaining the diversity of blood pressure among fishes of the world: A comparative phylogenetic approach.
Abstracts / Comparative Biochemistry and Physiology, Part A 146 (2007) S171–S188
Therefore, especially in the eye, the intricate interconnectivity of the multi-part multi-process oxygen delivery system still needs further investigation. doi:10.1016/j.cbpa.2007.01.383
A12.25 Circulatory physiology and haemotology of southern bluefin tuna (Thunnus maccoyii) T. Clark, R. Seymour, (University of Adelaide, Adelaide, Australia); P. Frappell, (La Trobe University, Melbourne, Australia) Haemoglobins (Hb) of several species of tuna are reported to display unusual O2 binding properties when faced with changes in blood temperature. Some species reportedly have temperature insensitive Hb-O2 binding, whereas others display a ‘reversed’ temperature effect such that an increase in temperature causes an increase in HbO2 affinity. We studied the haematological properties of a hitherto unstudied species, the southern bluefin tuna (Thunnus maccoyii), to examine the prevalence of this phenomenon amongst tuna species. Haematocrit and Hb concentrations were 49 ± 2% and 153 ± 8 g dl−1, respectively, which are comparable to values for mammals. At 0.5% CO2, the oxygen partial pressure at which Hb was 50% saturated (P50) was 2.89 kPa at 10 °C, 1.74 kPa at 23 °C and 1.95 kPa at 36 °C, indicating a reversed temperature effect between 10 °C and 23 °C (P < 0.05), and temperature insensitivity between 23 °C and 36 °C (P > 0.05). At 23 °C, the Hb displayed a marked root effect (10% decrease in O2 content from 7.8 to 7.0 mmol l−1 as CO2 increased from 0.5% to 1.5%) and had a large Bohr factor (?logP50/?pH = − 1.55). In another experiment, a newly designed implantable data logger has enabled us to obtain the first simultaneous measurements of heart rate (fH) and body temperature (Tb) in untethered tuna. In 18 °C water, Tb and fH remained within the ranges of 19.1–23.3 °C and 62–116 beats min−1, respectively. These values were at their lowest when the tuna were fasted, and at their highest during feeding and postprandial periods. This technology is helping to revolutionize our understanding of physiology and ecology of high performance fish in their natural environment. doi:10.1016/j.cbpa.2007.01.384
A12.26 Explaining the diversity of blood pressure among fishes of the world: A comparative phylogenetic approach H. Jourdan, (Institut des Sciences de l'Evolution (C.N.R.S. Université Montpellier 2) Département de Biologie Intégrative); D. Jones, M. Gardner, (Zoology Animal Care, University of British Columbia, Department of Zoology)
S179
Recent work based on necrophysiological determination of blood pressure among fish species reveals a wide range (10 to 130 mm Hg). We investigated whether this great variability was phylogenetically, environmentally, anatomically or physiologically determined. The relationships between such traits were studied in rockfishes (Sebastidae), scombrids (Scombroidei) and various orders of tropical marine teleosts, with the comparative method of phylogenetically independent contrasts (PIC). We used three new molecular phylogenies generated from cytochrome b gene partial sequences. There was no relationship between blood pressure and phylogeny, which might indicate that this is a rapidly evolving trait. Interestingly, rockfish species living in deeper (bathydemersal) environments had lower blood pressures than reef-associated species. In addition, in a more homogeneous (reef tropical) environment, we observed high blood pressures combined with high trophic levels. Besides, as might be expected, blood pressure was strongly correlated with heart mass, once data had been corrected for phylogeny. PIC analyses in rockfishes also revealed that blood pressure fitted better to the specific body size rather than to individual body size, suggesting that blood pressure might be adapted to the final adult size of the fish. Finally, we demonstrated an influence of partial endothermy on blood pressure in scombrids. doi:10.1016/j.cbpa.2007.01.385
A12.27 An investigation of the autonomic control and functional significance of heart rate variability during air-breathing in the jeju Hoplerythrinus unitaenitus D. McKenzie, (CNRS Montpellier); H. Campbell, E. Taylor, (Birmingham); M. Micheli, T. Rantin, (UFSCar); A. Abe, (UNESP Rio Claro) The jeju is a teleost fish with bimodal respiration that utilises a modified swimbladder as an air breathing organ. Airbreathing in fishes is associated with significant heart rate variability (HRV); exhalation with a sudden bradycardia followed by a marked tachycardia upon inhalation. In the jeju, instantaneous heart rate interval (derived from electrocardiogram R–R interval) varied more than twofold during this cycle. When exposed to profound aquatic hypoxia (water PO2 = 1 kPa) at 26 °C, jeju maintained metabolic rate at routine aerobic levels by air-breathing, which increased in frequency (fAB) from about 2 breaths per hour in aquatic normoxia to almost 20 in hypoxia. Mean heart rate (fH) did not change but the increased fAB elicited a significant increase in HRV. Treatment with propranolol (10−5 mol kg−1 intraperitoneal) did not affect mean fH but caused a further significant increase in HRV. Adrenergic tone, based upon mean R–R interval, was approximately 9%. Subsequent atropine treatment (10−5 mol kg−1) caused fH to more than double, and abolished all HRV associated with air-breathing. Cholinergic tone, based upon mean R–R interval, was over
Therefore, especially in the eye, the intricate interconnectivity of the multi-part multi-process oxygen delivery system still needs further investigation. doi:10.1016/j.cbpa.2007.01.383
A12.25 Circulatory physiology and haemotology of southern bluefin tuna (Thunnus maccoyii) T. Clark, R. Seymour, (University of Adelaide, Adelaide, Australia); P. Frappell, (La Trobe University, Melbourne, Australia) Haemoglobins (Hb) of several species of tuna are reported to display unusual O2 binding properties when faced with changes in blood temperature. Some species reportedly have temperature insensitive Hb-O2 binding, whereas others display a ‘reversed’ temperature effect such that an increase in temperature causes an increase in HbO2 affinity. We studied the haematological properties of a hitherto unstudied species, the southern bluefin tuna (Thunnus maccoyii), to examine the prevalence of this phenomenon amongst tuna species. Haematocrit and Hb concentrations were 49 ± 2% and 153 ± 8 g dl−1, respectively, which are comparable to values for mammals. At 0.5% CO2, the oxygen partial pressure at which Hb was 50% saturated (P50) was 2.89 kPa at 10 °C, 1.74 kPa at 23 °C and 1.95 kPa at 36 °C, indicating a reversed temperature effect between 10 °C and 23 °C (P < 0.05), and temperature insensitivity between 23 °C and 36 °C (P > 0.05). At 23 °C, the Hb displayed a marked root effect (10% decrease in O2 content from 7.8 to 7.0 mmol l−1 as CO2 increased from 0.5% to 1.5%) and had a large Bohr factor (?logP50/?pH = − 1.55). In another experiment, a newly designed implantable data logger has enabled us to obtain the first simultaneous measurements of heart rate (fH) and body temperature (Tb) in untethered tuna. In 18 °C water, Tb and fH remained within the ranges of 19.1–23.3 °C and 62–116 beats min−1, respectively. These values were at their lowest when the tuna were fasted, and at their highest during feeding and postprandial periods. This technology is helping to revolutionize our understanding of physiology and ecology of high performance fish in their natural environment. doi:10.1016/j.cbpa.2007.01.384
A12.26 Explaining the diversity of blood pressure among fishes of the world: A comparative phylogenetic approach H. Jourdan, (Institut des Sciences de l'Evolution (C.N.R.S. Université Montpellier 2) Département de Biologie Intégrative); D. Jones, M. Gardner, (Zoology Animal Care, University of British Columbia, Department of Zoology)
S179
Recent work based on necrophysiological determination of blood pressure among fish species reveals a wide range (10 to 130 mm Hg). We investigated whether this great variability was phylogenetically, environmentally, anatomically or physiologically determined. The relationships between such traits were studied in rockfishes (Sebastidae), scombrids (Scombroidei) and various orders of tropical marine teleosts, with the comparative method of phylogenetically independent contrasts (PIC). We used three new molecular phylogenies generated from cytochrome b gene partial sequences. There was no relationship between blood pressure and phylogeny, which might indicate that this is a rapidly evolving trait. Interestingly, rockfish species living in deeper (bathydemersal) environments had lower blood pressures than reef-associated species. In addition, in a more homogeneous (reef tropical) environment, we observed high blood pressures combined with high trophic levels. Besides, as might be expected, blood pressure was strongly correlated with heart mass, once data had been corrected for phylogeny. PIC analyses in rockfishes also revealed that blood pressure fitted better to the specific body size rather than to individual body size, suggesting that blood pressure might be adapted to the final adult size of the fish. Finally, we demonstrated an influence of partial endothermy on blood pressure in scombrids. doi:10.1016/j.cbpa.2007.01.385
A12.27 An investigation of the autonomic control and functional significance of heart rate variability during air-breathing in the jeju Hoplerythrinus unitaenitus D. McKenzie, (CNRS Montpellier); H. Campbell, E. Taylor, (Birmingham); M. Micheli, T. Rantin, (UFSCar); A. Abe, (UNESP Rio Claro) The jeju is a teleost fish with bimodal respiration that utilises a modified swimbladder as an air breathing organ. Airbreathing in fishes is associated with significant heart rate variability (HRV); exhalation with a sudden bradycardia followed by a marked tachycardia upon inhalation. In the jeju, instantaneous heart rate interval (derived from electrocardiogram R–R interval) varied more than twofold during this cycle. When exposed to profound aquatic hypoxia (water PO2 = 1 kPa) at 26 °C, jeju maintained metabolic rate at routine aerobic levels by air-breathing, which increased in frequency (fAB) from about 2 breaths per hour in aquatic normoxia to almost 20 in hypoxia. Mean heart rate (fH) did not change but the increased fAB elicited a significant increase in HRV. Treatment with propranolol (10−5 mol kg−1 intraperitoneal) did not affect mean fH but caused a further significant increase in HRV. Adrenergic tone, based upon mean R–R interval, was approximately 9%. Subsequent atropine treatment (10−5 mol kg−1) caused fH to more than double, and abolished all HRV associated with air-breathing. Cholinergic tone, based upon mean R–R interval, was over